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My Onan doesn't have spark.......

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NOSValves

Hey folks hope you can help. I'm pulling my hair out. I have a D160 that was retrofitted with a P220 previous to me purchasing it. I used it all this spring and summer but left it unused this fall for 6 to 8 weeks until the other day. It always started right up in the past. This time I couldn't get it to start it tried a couple times but then it would just roll over and over. I pulled the plugs and they were wet and full of soot. I cleaned them up and tried again with no luck. So I dug around and found all the service manual for trouble shooting the P220 Onan. The coil has the appropriate resistance of around 3 ohm primary from + to -  and 19K ohms between the secondaries. The control module goes from battery voltage to about 1 volt once per full revolution. I replaced the plugs with brand new and still no spark. I also hot wired the + side of coil from the battery with no change. 

 

 I'm out of ideas.and the winter snows are approaching fast.. 

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NOSValves

I fixed it inspite you helpful folks around here....it was the coil in spite of it testing as it should...

Edited by NOSValves

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leachy

what ohm reading should you get on the module? Does it change as you rotate the engine past TDC. Also if its a Hall effect does it have voltage rather then a permamnt magnet type sensor?

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leachy

Gents. I am still getting no spark from my coil. Is there any ohm reading check I can make to test the coil trigger mechanism? If I apply a meter to the trigger wires red and black that are connected to the coil psosts I get a very high K ohm reading and no change if I rotate the engine. If I apply voltage to the pos of the coil and rotate my engine with voltmeter on pos and engine ground still nothing. HELP!!

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leachy

If it is the trigger is there any easy way to get the flywheel off?? Do I need to time it before I remove it and do i mark it? What puller can I buy to get it off??? What size are the 4 bolts on the front face of the flywheel I think 1/2" head. Help Again!!

 

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NOSValves

You measure the control modules voltage at the positive terminal of the choke. As the flywheel rotates the voltage should go from battery voltage (12 or 13 VDC) to about 1 VDC as you rotate the flywheel. If you search the internet for a service manual for your onan it has instructions for testing the ignition system. But even those instructions are not fool proof. My coil tested fine but ended up being bad. But it had an obvious crack across the top. 

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NOSValves
3 hours ago, leachy said:

If it is the trigger is there any easy way to get the flywheel off?? Do I need to time it before I remove it and do i mark it? What puller can I buy to get it off??? What size are the 4 bolts on the front face of the flywheel I think 1/2" head. Help Again!!

 

 

 

What model tractor are you working on? 520?

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Off Track Horse

Question about testing the ignition coil:  Is the test done with the coil on the mower or with it removed?  The instructions read like it is still installed on the mower, but the picture shows it removed.  Also, my multimeter only has one Ohm setting.  How would I do the second part of the test?  Thank you in advance!

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Damien Walker

I have a couple of onans (actually both Toro Power Plus) one of which has just started running after 10 years in the shed and even longer stored outside in the rain (previous owner). Nothing wrong with onans hardware in my case, but the wiring is poor. I don't think the rain factor has affected things too badly but I have to say the quality of the electrical fittings is rather poor. If they had spent a little more on the connectors, things would not be so bad.

 

I'd check the coil as best as possible on the bench (mind your fingers and your heart pacemaker) and if there's no spark then that's it I suppose, but my problems were (and still are) wiring loom and connector based. I have replaced the main loom to engine connector pair...a number of wires had simply snapped off. I've gone for a more robust automotive equivalent but the things I am having the most trouble with are the connectors on the various interlock switches which have lost a significant amount of their grip. If the engine doesn't start, I wiggle those and off I go! I'd have replaced them and the microswitches if they weren't so dammed inaccessible and expensive. Battery out time when I have the spares.

 

It's a relatively pointless waste of time to refer to Wheelhorse (Toro?) wiring diagrams too....they are dreadful. The official diagram for my 518H is beyond polite description, the interlock wiring being a rats nest at best. Sit down with a pen and paper and laboriously redraw it and you'll find that it is actually trivial. The interlock system is essentially divided into two halves, one to inhibit the ignition under certain conditions, and the second to inhibit the starter. The only link between them occurs with the dual pto microswitch but they can be drawn separately. There are a number of other errors on similar vintage diagrams for the 312 and 416. For example, both these appear to show the engine to main loom connector except that the diagram shows all of the wiring with a bundle of wires going to one half of the connector pair and the other half going nowhere! On the 518H diagram they have not bothered to identify the wire colours on the engine loom (not Toro's responsibility I presume) so the owner's manual is not much help if you have engine wiring problems...and to add to this, Toro haven't used the same wiring colours in their half of the connector. Marvellous, with several detached wires, how do you know where to put them when you repair the thing....matching the colours is clearly not a good idea! Basically, I would accuse Toro of drawing something that is dead simple in the most unhelpful and inaccurate way!

 

There's another weird fault I had that probably was due to water ingress, one that had me convinced that I had screwed up the main connector rewire (different colour wires across the connector remember). It turned out to be a fault with the ignition switch which was causing the wrong interlock lights to illuminate. Swap to a spare switch and normality returned.

 

I wonder whether there's a marker for properly drawn circuit diagrams...!

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Damien Walker

Beautiful engine too, now that it is running. Have a Kohler Magnum 18 in my C175 which I swear by but it is very noisy. Ok so the difference may just be the exhaust (not perfect on the onan btw) but it is very quiet and smooth.

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lynnmor

Did you look thru the manuals section for a schematic that has been colorized?

 

Yes, colors are not exact across the 9 pin connector and you may find a few errors in wiring diagrams.

 

That Toro Power Plus means exactly nothing, it is a stock Onan with a couple of Toro stickers.

 

I have found that an Onan stored outdoors can be a real problem if disassembly is required, I will never buy one again.

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Damien Walker
On 3/6/2021 at 12:05 AM, lynnmor said:

Did you look thru the manuals section for a schematic that has been colorized?

 

Yes, colors are not exact across the 9 pin connector and you may find a few errors in wiring diagrams.

 

That Toro Power Plus means exactly nothing, it is a stock Onan with a couple of Toro stickers.

 

I have found that an Onan stored outdoors can be a real problem if disassembly is required, I will never buy one again.

Thanks Lynnmor, I didn't know about the marked up/colourised versions here. I've had a look and they look good (except that the one I looked at had the colours echoed across the main connector which is not true for my machine for some reason). Interesting that Toro found it necessary to publish a demystification guide (quite useful)...I would argue that if they had drawn the circuit diagrams properly, there would be no need for such  document. There's probably a good reason for this of course...they probably started with a diagram for a much earlier tractor with only two wires and gradually added to it instead of redrawing.

 

I agree about your 'stored outdoors and disassembly' comment. Mine is actually in reasonable condition (considering the treatment it received in it's earlier life), other than the exhaust tail pipe which is perforated and needs replacing. I think there's a thread on here about that somewhere but it's a fairly straight forward job, or would be if I could remove the exhaust system...I can't, it is seized in position. I'm hoping that running the engine for a while and heat cycling it a few times, might encourage it  to come loose and then I can get it on the bench and weld it with no risk to local paint work!

 

On the subject of the connectors and microswitches, I can buy good quality switches with 1/4" blade connectors (the originals are smaller) for next to nothing over here and if I replace the female connectors in the wiring loom too, all should be well, but I'll have to look a bit harder to find the self contained connectors that fit the switches directly and maintain the wire orientation, otherwise it will be individual wires and the consequential difficulties of maintaining the positioning in the event of a future dismantle!

 

Managed a run round the lawn tonight in the dark (LED headlights - that's a good mod - just 12W each) and I clearly have a number of problems to resolve still. The engine stops if I use the brakes...that's odd, there's no interlock  with the brakes/hydro control and the seat switch doesn't inhibit anything...but I'm getting there!

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lynnmor

The color added to many of the diagrams was done by a fellow member doing much to be helpful.  There are mistakes in the Demystification Guide and wire colors are not always correct. The fault lies with the original documents.

IMG_2113.JPG.ce50dc6236c5ffac35ce331fad6810fc.JPGIMG_2115.thumb.JPG.202327ccbe42987657eface3a76b7526.JPG

 

My opposite plug photo seems to have disappeared.

 

Apply penetrating oil to every fastener on the engine and the exhaust connections for days or weeks before attempting disassembly.  The muffler pipes stick down into the engine block and often corrode.  Damage from stuck fasteners and exhaust is the reason I don't want an Onan that was in the weather.  You do need to get the exhaust off for valve adjustment and other service.

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Damien Walker

OK, thanks for the photo, all help is appreciated!

 

Your photo is of the engine side of the pair on my spare machine and the colours are a little different. The middle and right columns are the same but the left column reading downwards is: White,  black, white. (not green,black, blue). The tractor side is different and as far as I can see with very few of the colours echoing across. Again as far as I can tell, the looms are unmolested save for the new main connector I have fitted to the tractor I'm working on...and at least on this machine, the colours broadly resemble yours! I have ordered new 1/4" blade microswitches for the pto interlock and will fit new connectors to suit when they arrive. I note I have bad contacts between the loom and the ignition switch too, so I think a new switch and connector might be wise here too.

 

I think the main issue for the 'Onan in the rain' issue is the mix of steel with alloy and tight tolerances. Steel and alloy are not good under such circumstances. My engine is running very smoothly (touch wood) probably as there's only 360hrs on the meter so there's no immediate dismantling need. I'm hoping that storing it dry, and heat cycling it, will loosen the exhaust. I did try the penetrating oil on everything method, and so far it has failed. I'll report back if I'm successful.

 

To echo back to the original thread, amazingly, the one problem I haven't suffered is spark problems, this thing wants to run!

 

 

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Handy Don

There is indeed a microswitch that detects "neutral" for the motion control and the brake pedal (if properly connected) will force the motion control to neutral.

Normally that switch's job is to prevent the starter from engaging unless the motion control is in neutral. Has it been circumvented or its wiring connections modified? There is also a parking brake detect switch that normally does nothing except light a dashboard indicator.

 

I must say that I've found the wiring diagrams more than adequate, given they were created many years before CAD systems with automatic layout features and that there were sometimes variations during production and even, horrors, by Previous Owners. If you are looking for perfect information on 30+ year old second, third, or fourth hand machinery you will nearly always be disappointed.

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Damien Walker
1 hour ago, Handy Don said:

There is indeed a microswitch that detects "neutral" for the motion control and the brake pedal (if properly connected) will force the motion control to neutral.

Normally that switch's job is to prevent the starter from engaging unless the motion control is in neutral. Has it been circumvented or its wiring connections modified? There is also a parking brake detect switch that normally does nothing except light a dashboard indicator.

 

I must say that I've found the wiring diagrams more than adequate, given they were created many years before CAD systems with automatic layout features and that there were sometimes variations during production and even, horrors, by Previous Owners. If you are looking for perfect information on 30+ year old second, third, or fourth hand machinery you will nearly always be disappointed.

 

Not on my 518H there isn't! It's long story that I will write up soon when the project is complete, but I have done a full rebuild and included power steering (wow, what an improvement!) and the inclusion of power steering left no room for the original hydro lever microswitch operating lug. The associated lever up/down movement from forwards to backwards has gone too. Consequently the hydro switch is bypassed..... and the parking brake switch is just wired into the dashboard lamp as you say. I have other problems to resolve first and so I have not investigated this in detail but there was a hint it was g-force related. ie touch the brakes gently and the engine is untroubled, brake more sharply, the hydro stops me dead and the engine dies regardless of what I then do with the brake pedal or hydro control......you would think you could catch it in time if it was electrical if you stopped doing whatever you did to cause the engine to falter, but the engine always dies. I'll sort it when I get to it..loose wire perhaps?.. but it always restarts instantly.

 

There's no need for a CAD system to draw these diagrams, they are not complex enough, but my main complaint with the 518H diagram lies with the interlock switch wiring...it's a rat's nest. Drawn with sensible conventions of 12V at the top GND at the bottom and the switches in line as they operate in sequence. would make it far easier to follow. It's no wonder that many people think vehicle electrics are for alchemists! As mentioned, the smaller tractors wonderfully show the loom connectors, but not where they fit in the circuit....there being nothing connected to the second half of the connector! I think they probably made a quick mod to an existing diagram to show the existence but forgot that someone might actually want to use it to troubleshoot a real machine....and their creation of the demystification guide could be a hint that they realised their mistake. I think it is probably likely that the design team weren't given enough time or budget to complete their work properly......and I know all about that from my own professional experience. I'm pretty confident my two machines were not tampered with....such horrors are usually obvious, yet the wire colour match is poor as I describe above. I suppose I should put my money where my mouth is and fully redraw the diagram to show how it could have been done...might do that when I've a spare moment.... let's see what sort of a mess I can make of it :)

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